Yes, if you plan to run the heater, having a second tank on hand is always worthwhile. We had a double carrier, but I kept the single regulator setup. The second tank was generally for the BBQ, but could easily swap for the trailer tank if one was out.
Bypass for the WH is built in. Pop the cover to the water heater cabinet (under the rear curbside dinette seat). Set the two valves at the WH to run water through the bypass hose. Make sure that you drain the tank, at least before the next frost sets in; the drain plug is behind the panel curbside.
A bit of family education to let people know that both taps are cold water, but the actual cold tap is filtered water (assumes you have the filter installed and not bypassed), and the hot tap provides raw unfiltered water.
2011 Jayco X19H (purchased 2015)
2008 Jayco 1007 PUP (purchased new, traded for the X19)
2012 Chev Traverse LT with TP